1. Field of the Invention
The present invention relates to a block copolymer consisting of segments of copolymer A, which is obtained by copolymerizing an aromatic vinyl monomer with a peroxycarbonate and has peroxy groups in its main polymer chain, and segments of (co)polymer B, which is different from copolymer A in the monomer composition and does not contain peroxy groups, and which block copolymer is useful for modifying resin and the like.
2. Related Art Statement
There have recently been predominantly investigated various methods for giving a functional group to a copolymer corresponding to the development of new technic of polymer blend. Particularly, a polymer having a functional group in its main polymer chain has a high reactivity and is a very attractive polymer.
For example, Plaste and Kautschuku, 26(3), 121 (1979) proposes a copolymer, which has been obtained by copolymerizing a peroxide having a (meth)acrylic type double bond with a (meth)acrylic acid ester monomer, and has peroxy groups in its main polymer chain.
Japanese Patent Application Publication No. 30,790/80 discloses, as a polymer containing peroxy bonds similarly to the above, a radically copolymerizable peroxycarbonate having an allyl type double bond represented by the following general formula (II) ##STR1## wherein R.sub.6 represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; R.sub.7 and R.sub.8 represent same or different alkyl groups having 1-4 carbon atoms; and R.sub.9 represents an alkyl group having 1-12 carbon atoms or a cycloalkyl group having 3-12 carbon atoms.
Copolymers of this radically copolymerizable peroxycarbonate having an allyl type double bond with vinyl chloride are disclosed in Japanese Patent Application Publication Nos. 26,617/82 and 26,619/82, a copolymer of this peroxycarbonate with ethylene-vinyl acetate is disclosed in Japanese Patent Laid-open Specification No. 139,514/81, a copolymer of this copolymer with diallyl phthalate is disclosed in Japanese Patent Application Publication No. 50,802/82, and a copolymer of this peroxycarbonate with vinyl acetate is disclosed in Japanese Patent Application Publication No. 42,083/82. The fact that the resulting copolymers have self-crosslinking property and graft performance has already been ascertained.
However, when it is intended to blend these copolymers with other resin, a grafting reaction occurs locally due to the absence of compatibility between the copolymer and the resin, and hence the resulting resin blend is poor in mechanical strength and is further poor in physical properties due to the phase separation.
Further, the radically copolymerizable peroxycarbonate represented by the above described general formula (II) as a good copolymerizability with a monomer having a non-conjugated double bond due to its allyl type double bond, but has a drawback that the peroxycarbonate does not copolymerize with a conjugated type monomer, such as aromatic vinyl monomer, (meth)-acrylic acid ester monomer or the like. In order to eliminate this drawback, there has been attempted to add a monomer copolymerizable with both the peroxycarbonate and the conjugated type monomer to the polymerization system. However, this method still has a drawback that aimed physical properties are not fully developed due to the addition of the copolymerizable monomer.
Recently, there have been developed methods for producing various block copolymers, and there has been attempted to produce a resin blend having novel properties by blending the resulting block copolymer with other resin, for example, under a melted state. According to this method, a large phase separation does not occur in the resin blend due to the properties of the block copolymer, and a homogeneous resin blend can be obtained. However, chemical bonds are not present at the interface of the blended resins, and therefore the resulting resin blend has such a drawback that the resin blend has a very low mechanical strength.
In order to eliminate those drawbacks, the inventors have disclosed in Journal of Technical Disclosure No. 83-6603 published by Japan Institute of Invention and Innovation a block copolymer consisting of segments of copolymer (a) and segments of copolymer (b), wherein only copolymer (a) contains peroxycarbonate groups. This block copolymer has such excellent properties that this block copolymer exhibits excellent dispersion stability in the blending with other resin and further exhibits high strength at the interface with other resin. However, this block copolymer still has the following drawbacks. That is, the double bond-containing peroxide to be used in the production of copolymer (a) is a radically copolymerizable peroxycarbonate represented by the general formula (II), and hence the monomer to be used in the production of copolymer (a) is limited to monomers having unconjugated double bonds, such as vinyl acetate, vinyl chloride and the like, and the use of such monomers having unconjugated double bond affects adversely the heat resistance, weather resistance, chemical resistance, electrical insulation property and the like in the resulting resin blend. Moreover, copolymer (b) is polystyrene, and therefore the use of the block copolymer having segments of copolymer (B) can give rigidity, surface gloss and the like to the resulting resin blend, but is difficult to give shock impact resistance, weather resistance and the like to the resin blend.